blastems

In developmental biology, a blastema is a mass of undifferentiated cells capable of growth and regeneration into organs or body parts. The term blastems is used informally as a plural; more widely accepted plurals are blastemas or blastemata.

Formation occurs after injury or amputation: resident cells de-differentiate or progenitor cells proliferate at the wound site, and a signaling-competent microenvironment is established. The blastema then grows and differentiates into tissues such as bone, muscle, and cartilage, guided by positional information within the regenerating limb or structure.

Key signaling pathways that regulate blastema formation and growth include FGF, Wnt, BMP, and SHH, along with retinoic acid signaling and interactions with the extracellular matrix and nerves. The immune system also modulates blastema formation, balancing inflammation and regeneration.

In nature, blastemas enable robust limb or fin regeneration in several species. Salamanders and axolotls form prominent limb blastemas that restore complex structures. Zebrafish regenerate fins via blastemal tissue. In mammals, digit-tip regeneration in mice and some humans shows a blastema-like structure but is limited compared with amphibians or fish.

Research on blastemas informs regenerative medicine and tissue engineering, aiming to recreate blastema-like environments in humans. Challenges include reproducing the full patterning of tissues, achieving adequate vascularization, and controlling growth to prevent tumor formation while preserving safety and precision.